Patent GB-1014071-A (GB)
Title: Explosive compositions
Inventor: GORDON WILLIAM EDWIN
IPC: C06B21/00
Filed: 1962-11-22
Abstract: In an explosive composition made by melting a mixture of ammonium nitrate and hexamethylenetetramine and rapidly cooling (see Division C1), the solidified melt contains the adduct (CH2)6N4 . 2NH4NO3.  The adduct may also be made by crystallization from an aqueous solution containing the components in the correct ratio; water must be removed at a temperature below about 40 DEG  C., e.g. by evaporation in a stream of air or under vacuum, by spray drying, or by azeotropic distillation with a solvent.ALSO:An explosive composition comprises a major proportion of ammonium nitrate and a minor proportion of a fuel, at least a portion of the ammonium nitrate being present as crystals of maximum dimension not exceeding 100 microns dispersed in a crystalline matrix comprising the fuel.  The matrix may also contain reaction products of ammonium nitrate and the fuel. The explosive may be used in small diameter cartridges and has low impact, heat, and friction sensitivity, but is highly sensitive to shock waves and has a high velocity of detonation. The composition may be formed by melting a <PICT:1014071/C1/1> mixture of ammonium nitrate and an organic fuel at below 170 DEG  C. and cooling rapidly. The ammonium nitrate may be in the form of coated "prills" or may contain up to 3% of water.  Preferred fuels are amines, amides, or imides, which may be unsubstituted or substituted; fuels specified are urea, dicyandiamide, and hexamethylenetetramine.  Secondary fuels which may be included are aluminium powder, finely divided carbon, dextrose, and fuel oil.  Addition of abeitic acid, methyl cellulose, or vegetable gums or starches causes the ammonium nitrate to crystallize in the form of small scales or plates.  The fuel may be melted with part of the ammonium nitrate and the cooled melt mixed mechanically with the remaining ammonium nitrate.  Apparatus for forming the explosive is shown in Fig. 3 and comprises heated roll 10 and cooled roll 12 which rotate in opposite directions, the clearance being adjustable at 28.  The speed and temperature of the rolls are also adjustable.  A pulverized blend of ammonium nitrate, hexamethylene tetramine, and fatty acid soap passes from hopper 36 on to roll 10, being spread out by idler roll 32; the material melts and is transferred to roll 12 on which it solidifies and is removed by doctor blade 42 into receiver 44.  The product may be comminuted, e.g. in a hammer mill, and stored in polyethylene bags.  Examples describe the preparation of compositions, one of which contains, in addition to the ingredients specified above, diatomaceous earth to improve moisture resistance. The density of the explosive may be adjusted to its optimum value for use as a blasting agent by passing the explosive again through the apparatus of Fig. 3, removing it from the hot roll, heating at about 90 DEG  C. and tamping into a cartridge, or by adding controlled amounts of water and bulking agents such as wood pulp or urea formaldehyde microballoons. Other additives to wet blasting agents are potassium dichromate as a catalyst, okra gum, sodium bicarbonate to reduce the density, wood flour, cellulose ether gum, ammonium nitrate, and sodium nitrate. The solidified melt contains an adduct of ammonium nitrate and hexamethylenetetramine (CH2)6N4.2NH4NO3 (see Division C2). Explosive compositions containing the adduct mixed with ammonium nitrate or other oxidizers and wood flour or finely divided anthracite coal are described.